Sex came out on top for men (85%) but was also the second-most-common theme for women (73%). The results are reversed when it comes to reporting dreams of being chased: 83% of women compared to 78% of men.

For both genders, dreams of falling were the third-most-common.

Women often dream that someone has died, or about being paralyzed by fear, about failing an exam or about encountering insects, spiders and snakes, the survey of 28,888 participants found. Men, on the other hand, are more likely to dream they fly or float in the air, they have magical powers or higher mental faculties, they kill someone or they travel to other planets and meet aliens.

That negative content is more common in women is consistent with findings that women, especially in adolescence, reported more nightmares than men, Nielsen said. Negative content occurs more frequently in both genders when they are between the ages of 20 and 30, when "the happiness index is at its lowest."

One result that surprised Nielsen was that the variety of subject matter in our dreams diminishes, rather than widens, the older we get.